Apparatus and method for hydroforming workpieces

ABSTRACT

An apparatus for hydroforming workpieces includes a first ( 11 ) and a second tool part ( 13 ) and a press device ( 1, 6, 7 ) which closes and holds together the tool parts during a forming cycle. The first tool part ( 11 ) is mounted in the press device ( 1, 6, 7 ). The second tool part ( 13 ) is disposed for insertion into and removal from the press device ( 1, 6, 7 ), for example with the aid of a conveyor ( 8 ). Further, the apparatus includes a supply of pressurized fluid ( 12 ) to the first tool part ( 11 ).

TECHNICAL FIELD

The present invention relaters to an apparatus for hydroformingworkpieces and comprises a forming tool with at least a first tool partand at least a second tool part, a press device for closing and holdingtogether the tool parts during a forming cycle, and means for supplyinga pressurised fluid to the tool during the forming cycle.

The present invention also relates to a method of hydroformingworkpieces and comprises the steps that at least one workpiece is placedin a tool which is closed, whereafter forming takes place and the formedworkpiece is removed from the tool

BACKGROUND ART

In this application, the term hydroforming is taken to signify a formingmethod in which a workpiece of sheeting or tubing is directly subjectedto a liquid under high pressure in order, under the action thereof, tobe formed in or against a tool. The fluid may, in this context, bewater, a water/oil emulsion, oil, etc. Hydroforming can achieveextremely high levels of accuracy and surface fineness in the processesworkpiece.

WO 95/31322 discloses an apparatus for hydroforming. This apparatusconsists of an outer frame in which there are disposed press devicesdisplaying short stroke length, but with extremely high pressing force.A tool unit is divided into a plurality of components and provided witha workpiece outside the press device and is also assembled outside thepress device. After assembly of the tool and the workpiece, the tool isinserted as a unit into the press device where it is dosed and heldtogether at the same time as the hydroforming operation takes place inthe tool. After completed forming, the tool is removed as a unit andemptied outside the press device. Thus, the press device serves thefunction of a separate tool locking means.

While the design and construction according to the above-mentioned PCTpublication may, in certain cases, function satisfactorily, it is,however, in many situations impractical and slow in operation. Thisapplies particularly to such situations where workpieces of relativelysimple shape are to be produced.

Problem Structure

The present invention has for its object to design the apparatusintimated by way of introduction such that it makes for extremelyrational production at low costs. The same applies also to the methodintimated by way of introduction. A further object of the presentinvention is to make it possible also to manufacture workpieces ofdifferent shapes in rapid sequence after each other.

Solution

The objects forming the basis of the present invention will be attainedin respect of the apparatus if this is characterized in that the firsttool part is mounted in the press device, while the second tool part isdisposed for insertion in the press device prior to a forming cycle, andfor removal from the press device after the forming cycle.

The objects forming the basis of the present invention will be attainedin respect of the method if this is characterized in that a first toolpart is held fixedly and immovably during a work cycle, that at least asecond tool part is provided with a workpiece, that the second tool partwith the workpiece is brought to a position in connection with the fisttool part and that the tool is closed by displacement of the second toolpart and the workpiece, whereafter the forming takes place.

Further advantages will be attained if the apparatus is also given oneor more of the characterizing features as set forth in appendedsubclaims 2 to 5 and if the method is also given one or more of thecharacterizing features as set forth in appended subclaims 7 and 8.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will now be described in greater detailhereinbelow, with reference to the accompanying Drawings. In theaccompanying Drawings:

FIG. 1 shows an apparatus according to the present invention seen in thedirection along which a tool part and a workpiece are fed into theapparatus;

FIG. 2 shows the apparatus of FIG. 1, seen in a direction from right toleft in FIG. 1;

FIG. 3 is a view corresponding to that of FIG. 1 of the apparatus with atool part inserted therein in the open state; and

FIG. 4 is a view corresponding to FIGS. 1 and 3 in a position where thetool is closed.

DESCRIPTION OF PREFERRED EMBODIMENT

In FIGS. 1 and 2, reference numeral 1 relates to a frame which isintended for absorbing extremely great forces. The frame 1 has an uppersection 2, a lower section 3 and side sections 4 and 5. The frame 1 isto be considered as a frame in a hydraulic press which has beendimensioned in such a manner that it can absorb forces of the order ofmagnitude of MN or more without undergoing any appreciable deformation.The technology for realising such a frame is well known in the art and,as a result, needs not be commented on in greater detail.

On the lower section 3 of the frame 1, there is disposed a forcegenerating unit 6 on which rests a lifting table 7. The force generatingunit is dimensioned to realise forces of the same order of magnitude asthe frame 1 is dimensioned to withstand. The force generating unit isdesigned for short stroke lengths, often a few or a few tens ofmillimetres, but for extremely great force and may include one or morehydraulic cylinders which each have a relatively slight ram surface areabut which together have the large ram surface area which is required forthe above-mentioned force generation. An assembly for the supply ofhydraulic fluid under pressure is connected to the force generating unit6 but will not be illustrated and described further. Correspondingly,the requisite control and regulation equipment is provided, but nor willthis be described in greater detail.

A conveyor 8 is provided for the insertion of a tool part into the frameto a position I on the lifting table 7 before a forming cycle and forremoving the tool part after the forming cycle. In its simplest form,the conveyor may be described as a pair of roller rails 9 which, withthe aid of suitable supports or mounting members 10, are disposed oneither side of the lifting table 7 at a height intended therefore inrelation to the lifting table 7 in its lower position of rest.

FIG. 1 shows, at reference numeral 11, a first tool part which, whilenaturally being replaceable, is to be considered as immobile andpermanently mounted in the frame 1 during operation. The first tool parthas an inlet 12 for the supply of pressurised fluid, preferably a liquidwhich is used for forming a workpiece and which, in such instance, ispreferably in direct action and contact with the workpiece.

In its simplest form, the first tool part 11 has a planar underside withone or more outlets for the above-mentioned pressurised fluid. If theworkpiece, prior to a forming operation, is a flat sheet, his design ofthe underside will realise an adequate sealing against the workpiece inorder to build up, between the workpiece and the underside, a sufficientfluid pressure for forming the workpiece.

FIG. 2 shows a second or lower tool part 13 which, in its upper surface,has a mould cavity 14. The second tool part 13 is movable between aposition I located outside the frame 1 where a workpiece is placed onthe tool part, to a position II located in the frame 1 in connectionwith the first tool part 11, the position II also being shown in FIG. 3.In order to achieve this mobility of the second tool part, this toolpart may suitably be provided with roller means 15, with rollers whichrest on the roller rails 9.

As will be apparent from FIG. 2, the conveyor 8 (i.e. in this embodimentthe roller rails 9) may be disposed to be through-going in the frame 1so that the lower tool part 13 may be displaced from the position Iillustrated in FIG. 2 to a position II (FIG. 3) located interiorly inthe frame 1, and to a position III in FIG. 2 located to the right of theframe 1. The reason for this is that, in position I, a workpiece isapplied on the second tool part 13, in position II, the work cycle iscarried out interiorly in the frame 1, and in position II, the finishedworkpiece is removed from the second tool part. The second tool part maythen be recycled in one suitable way or another back to position II orpossibly be provided with a new workpiece in position III and returnedto position II for processing and thereafter to position I for removalof the workpiece.

The present invention also encompasses the possibility of employing aplurality of variously designed second or lower tool parts which havemould cavities of different shapes. This implies that the workpieces,after the forming cycle, will have different appearances. This ispossible in that the first tool part may in principle be designed with atotally planar lower surface which, prior to the forming cycle with thetool dosed (according to FIG. 4), sealingly abuts against the upper sideof the workpiece.

In FIG. 3, the second tool part 13 is shown inserted in the frame 1before the force generating unit 6 has lifted the lifting table 7 upinto abutment against the underside of the second tool part 13, i.e.before the tool is closed. In practice, only the play between the upperside of the lifting table 7 and the lower side of the second tool part13 which is sufficient to make possible rolling-in of the second toolpart 13 to the position shown in FIG. 3 is required. In practice, aclearance or play of one or a few millimetres would probably besufficient

In FIG. 3, a workpiece 16 in the form of a substantially planar sheethas been shown resting on the second tool part 13. In the Figure, edgeportions of the workpiece 16 extend outside the periphery of the secondtool part. On the other hand, in a practical embodiment it is probablethat the second tool part 13 would be provided with retainer memberswhich, in a horizontal direction, prevent the workpiece 16 from slidingon the upper side of the tool part. In such an embodiment, the edgeportions of the workpiece 16 would be located inside the outer peripheryof the second tool part. Such retainer members for the workpiece may bedesigned as an outer frame around the periphery of the second tool part,but may, for example, also comprise magnets, suction devices or thelike. Further, there are provided sealing means around the periphery ofthe mould cavity 14 which, when the tool is closed, press the workpiece16 into sealing abutment against the first tool part 11.

In FIG. 4, the force generating unit 6 has been activated so that thelifting table 7 has been brought into abutment against the underside ofthe second tool part 13 and its roller means 15 have been lifted fromthe roller rails 9. In this position, the workpiece 16 is pressed withgreat force between the first and second tool parts, sealing takingplace between the upper side of the workpiece 16 and the lower side ofthe first tool part 11. In the position according to FIG. 4, pressurisedfluid is supplied via the inlet 12 to the interface between the upperside of the workpiece 16 and the lower side of the first tool part 11,whereupon the workpiece bulges downwards into the mould cavity 14 (FIG.2) in the second tool part 13. The supply of pressure medium to theupper side of the workpiece 16 is carried out for such a length of timeand with such great volume that the workpiece is pressed hard downagainst the defining walls of the mould cavity 14 and with such greatforce that the workpiece is shaped in accordance with the shape of themould cavity with consummate accuracy.

Once the forming of the workpiece has taken place according to FIG. 4,the lifting table 7 is once again lowered, whereafter the second toolpart 13 and the finished workpiece are removed from the frame 1, wherethe second tool part is released from the workpiece. Thereafter, thecycle is repeated with the same or an identical or otherwise formedsecond tool part.

In the foregoing, the underside of the first tool part has beendescribed as being substantially planar. However, according to thepresent invention, it is possible also to provide this tool part with amould cavity which in such an event, would correspond to the mouldcavity 14. In this alternative, the second tool part 13 also has aninlet for pressurised fluid which is employed for pressing the workpieceinto the mould cavity which is placed in the first tool part. If, insuch instance, the area of the mould cavity in the upper tool part isconsiderably smaller than the area of the mould cavity 14 in the secondtool part, the workpiece may first be pressed in an upward directionunder the action of pressurised fluid which is supplied via the secondtool part, whereafter a second forming takes place in a downwarddirection by means of pressurised fluid which is supplied via the inlet12 in the first tool part.

As an alternative to the mutual placing of the first and second toolparts 11 and 13, respectively, as shown on the Drawings, it is alsopossible to provide an arrangement where the plane of division betweenthe tool parts is vertical, i.e. the workpiece stands upright instead oflying horizontally.

The present invention should not be considered as restricted to thatdescribed above and shown on the drawings, many modifications beingconceivable without departing from the scope of the appended Claims.

What is claimed is:
 1. Apparatus for hydroforming workpieces,comprising: a frame defining a work space; a first tool part fastened tothe frame in the work space; a second tool part; conveyor means forinserting the second tool part in a work position in the work spaceadjacent the first tool part prior to a forming cycle, and for removalof the second tool part from the work space after the forming cycle; amold cavity in at least one of the first and second tool part; means forlocating a workpiece between the first and second mold part; means forurging the first and second tool parts together with the workpiecetherebetween in the forming cycle; and means for supplying pressurizedfluid to the workpiece between the first and second tool parts throughat least one of said first and second tool parts for forming theworkpiece in said forming cycle, wherein said means for urging maintainsthe first and second tool parts together in the forming cycle. 2.Apparatus according to claim 1, wherein said means for supplyingpressurized fluid is connected to said first tool part.
 3. Apparatusaccording to claim 1, including a conveyor for inserting the second toolpart in a work position in the work space, wherein the first and secondtool parts are closable under the action of a press device.
 4. Apparatusaccording to claim 3, wherein the first tool part is immobile in thepress device seen in its working direction.
 5. Apparatus according toclaim 3, wherein the work direction of the press device is substantiallyvertical, and wherein the press device includes lifting means forlifting the second tool part to a forming position in cooperation withthe first tool part.
 6. Apparatus according to claim 1, wherein theworkpiece is carried by the second tool part, and including sealingmeans for providing a seal between the first tool part and second toolpart during the forming cycle.
 7. Apparatus according to claim 1,including a mold cavity in the first tool part.
 8. Apparatus accordingto claim 1, including a mold cavity in the first and second tool part,wherein one of said mold cavities has a bigger cross sectional area thanthe other, the cross sectional areas being parallel to the plane of theworkpiece between forming thereof.
 9. Apparatus according to claim 1,wherein said means for urging comprises power means for forcibly urgingthe second tool part against the first tool part, with the workpiecebeing firmly clamped therebetween during the forming cycle. 10.Apparatus according to claim 2, wherein said means for supplyingpressurized fluid supplies pressurized fluid to the first tool part anddistributes said fluid to a surface of the workpiece facing the firsttool part during the forming cycle.
 11. Method for hydroformingworkpieces, which comprises: fastening a first tool part to a frame in awork space of said frame; inserting a second tool part in a workposition by a conveyor means in said work space adjacent the first toolpart prior to a forming cycle; providing a mold cavity in at least oneof the first and second tool parts; locating a workpiece between thefirst and second tool parts; urging the first and second tool partstogether with the workpiece therebetween in the forming cycle; andsupplying pressurized fluid to the workpiece between the first andsecond tool parts through at least one of said first and second toolparts for forming the workpiece in said forming cycle, wherein saidmeans for urging maintains the first and second tool parts together inthe forming cycle.
 12. Method according to claim 11, including the stepof removing the second tool part from the work space after the formingcycle by said conveyor means.
 13. Method according to claim 11,including connecting a means for supplying pressurized fluid to saidfirst tool part.
 14. Method according to claim 11, including holding thefirst tool part fixed and immobile during said forming cycle and movingthe second tool part and workpiece to the first tool part in the formingcycle.
 15. Method according to claim 11, including carrying theworkpiece by the second tool part, and sealing the first tool part andsecond tool part together during the forming cycle.
 16. Method accordingto claim 11, including providing a mold cavity in the first tool part.17. Method according to claim 11, including providing a mold cavity inthe first and second tool part, wherein one of said mold cavities has abigger cross sectional area than the other, the cross sectional areasbeing parallel to the plane of the workpiece before forming thereof. 18.Method according to claim 11, wherein said means for supplyingpressurized fluid supplies pressurized fluid to the first tool part anddistributes it to a surface of the workpiece facing the first tool partduring the forming cycle.
 19. Method according to claim 11, includingforcibly urging the second tool part against the first tool part bypower means with the workpiece firmly clamped therebetween during theforming cycle.